12 
SEXUAL SELECTION. 
Part II. 
male, which are absent in the female. These tentacles 
are prolongations of the true skin, and therefore are not 
homologous with the stiff hairs of the former species; but 
it can hardly be doubted that both serve the same 
purpose. What this purpose may be it is difficult to 
conjecture ; ornament does not here seem probable, but 
we can hardly suppose that stiff hairs and flexible fila- 
ments can be useful in any ordinary way to the males 
alone. The Monacantlius scopag, which was shewn to me 
in the British Museum by Dr. Gunther, presents a nearly 
analogous case. The male has a cluster of stiff, straight 
spines, like those of a comb, on the sides of the tail ; and 
these in a specimen six inches long were nearly an inch 
and a half in length ; the female has on the same place 
a cluster of bristles, which may be compared with those 
of a tooth-brush. In another species, the M. peronii, the 
male has a brush like that possessed by the female of 
the last species, w'hilst the sides of the tail in the female 
are smooth. In some other species the same part of the 
tail can be perceived to be a little roughened in the 
male and perfectly smooth in the female ; and lastly in 
others, both sexes have smooth sides. In that strange 
monster, the Chimasra monstrosa, the male has a hook- 
shaped bone on the top of the head, directed forwards, 
with its rounded end covered with sharp spines ; in the 
female “ this crown is altogether absent,” but what its 
use may be is utterly unknown . 17 
The structures as yet referred to are permanent in the 
male after he has arrived at maturity ; but with some 
Blennies and in another allied genus 18 a crest is deve- 
loped on the head of the male only during the breed- 
U F. Buckland, in 1 Land and Water,’ July, 1868, p. 377, with a 
figure. 
18 Dr. Giintlier, £ Catalogue of Fishes,’ vol. iii. p. 221 and 240. 
